Follow up...
I contacted Critical Dimensions. They stated it was probably a feature of my receiver, but offered to mill a relief cut in the rails. The other solution they offered was a set of washers.
As it turns out, even if the pad were not there, the sides of the receiver are not parallel to the sight/bore. There is about a .025” overall taper (side to side) on the receiver. That taper is probably good for 8-9” of windage error at 50 yards for laser if I did the math right.
So, I picked through the washers. I had one that was within a few .001” of the thickness necessary to put the rail in alignment with the sight.
I am really impressed with CD's customer support. Some people would have said “it’s your receiver”, and left it at that. Instead, they offered a number of solutions.
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